Shea butter, sal fat, allanblackia fat, palm oil and an interesterified oil obtained by selectively introducing a saturated fatty acid into 1,3-positions of an oil-and-fat rich in oleic acid at 2-position of the triglyceride such as high oleic sunflower oil, contains a large amount of SUS (symmetric triglycerides) such as StOSt, POSt, and POP (St: stearic acid, O: oleic acid, P: palmitic acid). From these oils-and-fats containing SUS, various oils-and-fats for chocolate similar to cocoa butter, cocoa butter substitutes, are produced.
While the oils-and-fats can be used as it is for making confectionary such as chocolate, cream and margarine, the solvent fractionation using hexane or acetone has been widely performed so that the concentration of SUS of the crystal fraction fractionated is further increased in content.
Such a crystal fraction rich in SUS can be one of the high quality cocoa butter substitutes having high snappiness, heat resistance and shape keeping property, and a good melting speed in the mouth with a cool sensation, for chocolate.
Solvent fractionation is extremely good in the separation efficiency of fractionation into a crystal fraction and a liquid fraction. However, since a solvent is used, there are problems that the handling thereof requires sufficient attention in terms of safety and health, and that the process cost is somewhat expensive because of requirements for large-scale equipment and removal of the solvent.
For this reason, recently, a dry fractionation method which is easy and highly safe has been developed.
The dry fractionation method includes completely melting a raw material oil-and-fat by heating generally without using a solvent, cooling the molten oil-and-fat in a crystallization tank with stirring in order to crystallize the high melting point fraction, then separating the oil-and-fat into a crystal fraction and a filtrate (unsolidified low melting point fraction) by pressing and/or filtration, and this method has been merely utilized in fractionating a lauric oil-and-fat and palm oil. That is, the conventional crystallization method with stirring was not applicable to the fractionation of an oil-and-fat having a SUS content of 30% by weight or more. If such an oil-and-fat is subjected to the stirring method to obtain a fraction richer in a SUS content, it is difficult to separate the oil-and-fat into a crystal fraction and a filtrate successively. Because the crystal amount is too much and fine crystals are precipitated throughout the oil-and-fat, and thereby the entire oil-and-fat becomes too high in viscosity or is solidified and cannot be transported with a pump to the subsequent press-filtering step. This tendency is particularly remarkable in shea butter, sal fat and the like containing a large amount of StOSt, and the stirring method has been difficult to apply for these oils-and-fats.